Methods for removing unsaturated aliphatic hydrocarbons from a hydrocarbon stream using activated carbon

ABSTRACT

Disclosed is a method for removing unsaturated aliphatic compounds from a hydrocarbon feed stream by contacting the hydrocarbon feed stream with activated carbon to produce a hydrocarbon effluent stream having a lower unsaturated aliphatic content relative to the hydrocarbon feed stream. The hydrocarbon feed stream comprises an aromatic compound, a nitrogen compound, and an unsaturated aliphatic compound.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/424,822 filed on Dec. 20, 2010.

FIELD OF THE INVENTION

This invention relates to methods for removing unsaturated aliphaticcompounds from a hydrocarbon stream. More particularly, this inventionrelates to use of activated carbon to remove unsaturated aliphatics froma hydrocarbon stream comprising aromatics.

BACKGROUND OF THE INVENTION

The use of molecular sieves as catalysts in aromatic conversionprocesses are well known in the chemical processing and refiningindustry. Aromatic conversion reactions of considerable commercialimportance include the alkylation of aromatic compounds such as in theproduction of ethyltoluene, xylene, ethylbenzene, cumene, or higheralkyl aromatics and in disproportionation reactions such as toluenedisproportionation, xylene isomerization, or the transalkylation ofpolyalkylbenzenes to monoalkylbenzenes. Often the feedstock to such anaromatic conversion process will include an aromatic component, i.e.alkylation substrate, such as benzene, and a C2 to C20 olefin alkylatingagent or a polyalkyl aromatic hydrocarbon transalkylating agent. As usedherein, terms such as “C4”, “C5”, “C6”, etc. designate the number ofcarbon atoms per molecule of a hydrocarbon or hydrocarbon specie. In thealkylation zone, the aromatic feed stream and the olefinic feed streammay be reacted over an alkylation catalyst to produce alkylatedaromatics, e.g. cumene or ethylbenzene. A portion or all of thealkylation substrate may be provided by other process units includingthe separation section of a styrene process unit. Polyalkylated benzenesare separated from monoalkylated benzene product and recycled to atransalkylation zone and contacted with benzene over a transalkylationcatalyst to yield monoalkylated benzenes and benzene.

Catalysts for aromatic conversion processes generally comprise zeoliticmolecular sieves. Examples include, zeolite beta (U.S. Pat. No.4,891,458); zeolite Y, zeolite omega and zeolite beta (U.S. Pat. No.5,030,786); X, Y, L, B, ZSM-5 and Omega crystal types (U.S. Pat. No.4,185,040); X, Y, ultrastable Y, L, Omega, and mordenite zeolites (U.S.Pat. No. 4,774,377); and UZM-8 zeolites (U.S. Pat. No. 6,756,030 andU.S. Pat. No. 7,091,390). It is known in the art that the aromatic feedstream to aromatic conversion processes often contains nitrogencompounds, including weakly basic organic nitrogen compounds such asnitriles, that can, even at ppm and ppb levels, cumulatively act topoison the downstream aromatic conversion catalysts such as aromaticalkylation catalysts and significantly shorten their useful life. Avariety of guard beds having clay, zeolite, or resin adsorbents toremove one or more types of nitrogen compounds from an aromatichydrocarbon stream upstream of an aromatic conversion process are knownin the art. Examples include: U.S. Pat. No. 7,205,448; U.S. Pat. No.7,744,828; U.S. Pat. No. 6,297,417; U.S. Pat. No. 5,220,099; WO00/35836; WO 01/07383; U.S. Pat. No. 4,846,962; U.S. Pat. No. 6,019,887;and U.S. Pat. No. 6,107,535.

It has recently been discovered that unsaturated aliphatic hydrocarbonssuch as olefinic compounds, and particularly diolefins, can shorten theeffective life of adsorbents, e.g. nitrogen adsorptive zeolites ormolecular sieves, used in nitrogen guard beds that are applied tovarious process streams, including aromatic hydrocarbon feeds upstreamof an aromatic conversion process such as alkylation. These unsaturatedaliphatic, e.g. olefinic, compounds are present in aromatic processstreams contaminated with nitrogen compounds, including benzene streamsgenerated in styrene process separation sections and other streamsrequiring removal of the nitrogen compounds prior to being contactedwith a catalyst or other material susceptible to nitrogen poisoning. Thepresence, in particular, of highly unsaturated olefinic compounds, e.g.C4-C6 diolefins, in aromatic streams having nitrogen compoundcontaminants, adversely impacts the performance of nitrogen adsorptivematerials. Without being bound by theory, it is believed that theolefinic compounds and/or other unsaturated aliphatic compounds mayshorten the life of the nitrogen adsorbent by competing with thenitrogen compounds for the adsorption sites and/or reacting, e.g. witharomatics such as benzene, to form heavy reaction products that depositon the nitrogen guard bed adsorbent.

SUMMARY OF THE INVENTION

The invention relates to methods for removing unsaturated aliphaticcompounds, including olefins and/or diolefins that are present in anaromatic hydrocarbon stream. In an embodiment, the invention enableslonger life of the adsorbent in a downstream nitrogen removal zone,which minimizes the need to regenerate or replace the nitrogenadsorbent.

In an embodiment, the invention is a method for treating a hydrocarbonfeed stream comprising an aromatic compound, a nitrogen compound, and anunsaturated aliphatic compound. The method comprises contacting thehydrocarbon feed stream with activated carbon, at contacting conditionscomprising a temperature of at least about 50° C. and the presence ofwater in an amount of at least about 50 ppm relative to the hydrocarbonfeed stream on a weight basis, to remove the unsaturated aliphaticcompound and produce a treated hydrocarbon stream.

In another embodiment, the invention is a method for producing analkylated benzene compound. The method comprises (i) contacting ahydrocarbon feed stream comprising benzene, an organic nitrogencompound, and a diolefin compound with activated carbon to remove thediolefin compound and produce a treated hydrocarbon stream; (ii) passingat least a portion of the treated hydrocarbon stream to a nitrogenremoval zone, which produces an alkylation substrate stream; and (iii)passing at least a portion of the alkylation substrate stream to analkylation zone, which produces the alkylated benzene compound.

The combination of removing one or more unsaturated aliphatic compoundsand removing nitrogen from aromatic streams can extend the life of thecatalyst in the alkylation zone and/or the life of an adsorbent in anitrogen removal zone, which may be located between the unsaturatedaliphatic removal zone and the alkylation zone. Further, the removal ofthe reactive unsaturated aliphatic hydrocarbons, such as, olefins and/ordiolefins, may minimize the loss of benzene and other desired aromaticcompounds to be recycled and reacted.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to methods for treating a hydrocarbon feed streamwherein one or more unsaturated aliphatic hydrocarbon compounds areremoved from the feed stream by activated carbon to produce a treatedhydrocarbon stream. The treated hydrocarbon stream has a lowerunsaturated aliphatic hydrocarbon content relative to the hydrocarbonfeed stream. The hydrocarbon feed stream of the invention comprises anaromatic compound, a nitrogen compound and an unsaturated aliphaticcompound.

The aromatic hydrocarbon compound may be selected from the groupconsisting of benzene, naphthalene, anthracene, phenanthrene, andsubstituted derivatives thereof, with benzene and its derivatives beingpreferred aromatic compounds. The aromatic compound may have one or moreof the substituents selected from the group consisting of alkyl groupshaving from 1 to about 20 carbon atoms, hydroxyl groups, and alkoxygroups whose alkyl group also contains from 1 up to 20 carbon atoms.Where the substituent is an alkyl or alkoxy group, a phenyl group canalso be substituted on the alkyl chain.

Although unsubstituted and monosubstituted benzenes, naphthalenes,anthracenes, and phenanthrenes are most often used in the practice ofthis invention, polysubstituted aromatics also may be employed. Examplesof suitable alkylatable aromatic compounds in addition to those citedabove include biphenyl, toluene, xylene, ethylbenzene, propylbenzene,butylbenzene, pentylbenzene, hexylbenzene, heptylbenzene, octylbenzene,etc.; phenol, cresol, anisole, ethoxy-, propoxy-, butoxy-, pentoxy-,hexoxybenzene, and so forth. Sources of benzene, toluene, xylene, and orother feed aromatics include product streams from naphtha reformingunits, aromatic extraction units, recycle streams from styrene monomerproduction units, and petrochemical complexes for the producingpara-xylene and other aromatics. The hydrocarbon feed stream maycomprise more one or more aromatic hydrocarbon compounds. In anembodiment, the concentration of the aromatic compound in thehydrocarbon feed stream ranges from about 5 wt % to about 99.9 wt % ofthe hydrocarbon feed. In another embodiment, the hydrocarbon feed streamcomprises between about 50 wt % and about 99.9 wt % aromatics, and maycomprise between about 90 wt % and about 99.9 wt % aromatics.

The hydrocarbon feed stream nitrogen compound may comprise one or moreorganic nitrogen compounds. Organic nitrogen compounds typically includea larger proportion of basic nitrogen compounds such as indoles,pyridines, quinolines, diethanol amine (DEA), morpholines includingN-formyl-morpholine (NFM) and N-methyl-pyrrolidone (NMP). Organicnitrogen compounds may also include weakly basic nitriles, such asacetonitrile, propionitrile, and acrylonitrile. As discussed below, theinstant invention does not require but encompasses use of an optionalnitrogen removal zone which reduces the nitrogen content of ahydrocarbon stream.

In an embodiment, the hydrocarbon feed stream has a nitrogen contentranging from about 1 ppm-wt to about 10 ppm-wt. In another embodiment,the concentration of organic nitrogen compounds in the hydrocarbon feedranges from about 30 ppb-wt (parts per billion by weight) to about 1mole % of the hydrocarbon feed; the concentration of organic nitrogencompounds may range from about 100 ppb-wt to about 100 ppm-wt (parts permillion by weight) of the hydrocarbon feed. In an embodiment, theconcentration of weakly basic organic nitrogen compounds such asnitriles in the hydrocarbon feed ranges from about 30 ppb-wt to about100 ppm-wt of the hydrocarbon feed.

The hydrocarbon feed stream comprises one or more unsaturated aliphaticcompounds, including unsaturated cyclic hydrocarbons and straight andbranched chain olefinic hydrocarbons (olefins) having one or more doublebonds. Thus, as used herein the terms “olefins” and “olefinichydrocarbons” include diolefin compounds. In an embodiment, theunsaturated aliphatic compound is an olefin compound, and theunsaturated aliphatic compound may be a diolefin compound. In anembodiment, the unsaturated aliphatic compound is one or more diolefincompounds having four, five, or six carbon atoms per molecule, i.e. theunsaturated aliphatic compound may be selected from the group ofdiolefins consisting of C4 diolefins, C5 diolefins, C6 diolefins, andmixtures thereof. In another embodiment, the diolefin compound isselected from the group consisting of butadienes, pentadienes,methylbutadienes, hexadienes, methylpentadienes, dimethylbutadienes,acetylenes, and mixtures thereof.

In an embodiment, the concentration of diolefin compounds in thehydrocarbon feed ranges from about 30 ppb-wt to about 3000 ppm-wt of thehydrocarbon feed; and the concentration of diolefin compounds may rangefrom about 50 ppb-wt to about 2000 ppm-wt of the hydrocarbon feed. Thehydrocarbon feed stream may comprise other olefins such as mono-olefins.Typically, the overall concentration of all olefins in the hydrocarbonfeed stream will be no more than 1.0 wt-% olefins.

In an embodiment, the aromatic compound comprises benzene, the nitrogencompound comprises an organic nitrogen compound, and the unsaturatedaliphatic compound comprises an olefin compound. In another embodiment,the aromatic compound comprises benzene, the nitrogen compound comprisesan organic nitrogen compound, and the unsaturated aliphatic compoundcomprises a diolefin compound, optionally the diolefin compound has fourto six carbon atoms per molecule.

The method includes the use of activated carbon. Activate carbon is wellknown in the art and may be derived from various sources includingpetroleum coke, coal, wood, and shells, such as coconut shells, usingcarbonization and/or activation process steps. Activation may beaccomplished, e.g. by thermal treatment under an atmosphere of CO₂, H₂Oand mixtures thereof, by chemical treating steps, and combinationsthereof Suitable activated carbon is commercially available and may beobtained for example from Calgon.

The hydrocarbon feed stream to be treated is contacted with activatedcarbon at contacting conditions to remove one or more unsaturatedaliphatic compounds and produce a treated hydrocarbon stream. Theunsaturated aliphatic compounds may be removed from the hydrocarbonstream by various mechanisms such as adsorption, reaction, and reactiveadsorption with the adsorbent. The treated hydrocarbon stream has alower unsaturated aliphatic compound content relative to the unsaturatedaliphatic compound content of the hydrocarbon feed stream.

The contacting conditions include a temperature of at least about 50° C.and the presence of water in an amount of at least about 50 ppm relativeto the hydrocarbon feed stream on a weight basis. Water may be presentin an amount equal to or beyond the saturation point of the hydrocarbonfeed stream at the contacting conditions. In an embodiment, water ispresent in an amount of at least about 250 ppm relative to thehydrocarbon feed stream on a weight basis. In another embodiment, wateris present in an amount ranging from about 300 ppm to about 800 ppmrelative to the hydrocarbon feed stream on a weight basis, and water maybe present in an amount ranging from about 450 ppm to about 700 ppmrelative to the hydrocarbon feed stream on a weight basis. The amount ofwater during contacting may be controlled in any suitable manner. Forexample, the water content of the hydrocarbon feed may be monitored andcontrolled by drying and/or adding water or water generating compoundsto the feed stream. Water or water generating compounds may beintroduced as a separate stream to the contacting step, and the feedstream may be dried to a consistent water level while water or watergenerating compounds are added to obtain the desired content. In anembodiment, the contacting temperature ranges from about 100° C. toabout 300° C. In another embodiment, the contacting temperature rangesfrom about 125° C. to about 300° C.; and the contacting temperature mayrange from about 150° C. to about 300° C.

In an embodiment, the amount of water is at least about 50 ppm relativeto the hydrocarbon feed stream on a weight basis and the contactingtemperature: (i) is at least about 50° C.; (ii) ranges from about 100°C. to about 300° C.; (iii) ranges from about 125° C. to about 300° C.;or (iv) ranges from about 150° C. to about 300° C. In an embodiment, theamount of water is at least about 250 ppm relative to the hydrocarbonfeed stream on a weight basis and the contacting temperature: (i) is atleast about 50° C.; (ii) ranges from about 100° C. to about 300° C.;(iii) ranges from about 125° C. to about 300° C.; or (iv) ranges fromabout 150° C. to about 300° C. In another embodiment, the amount ofwater equals or exceeds the saturation point of the hydrocarbon feedstream at the contacting conditions and the contacting temperature: (i)is at least about 50° C.; (ii) ranges from about 100° C. to about 300°C.; (iii) ranges from about 125° C. to about 300° C.; or (iv) rangesfrom about 150° C. to about 300° C. In a further embodiment, the amountof water ranges from about 300 ppm to about 800 ppm relative to thehydrocarbon feed stream on a weight basis and the contactingtemperature: (i) is at least about 50° C.; (ii) ranges from about 100°C. to about 300° C.; (iii) ranges from about 125° C. to about 300° C.;or (iv) ranges from about 150° C. to about 300° C. In an embodiment, theamount of water ranges from about 450 ppm to about 700 ppm relative tothe hydrocarbon feed stream on a weight basis and the contactingtemperature: (i) is at least about 50° C.; (ii) ranges from about 100°C. to about 300° C.; (iii) ranges from about 125° C. to about 300° C.;or (iv) ranges from about 150° C. to about 300° C. Optionally, thecontacting conditions may further include a pressure from about 34.5kPa(g) to about 4136.9 kPa(g). In an embodiment, the contacting isconducted with the feed in the liquid phase or partial liquid phase. Gasphase contacting may be used.

Bromine Index is commonly used to assess the unsaturated aliphaticcontent, including olefins and diolefins, of hydrocarbon mixtures. In anembodiment, the invention removes at least about 50% of the unsaturatedaliphatic compounds from the hydrocarbon feed stream. That is, in thisembodiment, the treated hydrocarbon stream has a Bromine Index of atmost about 50% of the Bromine Index of the hydrocarbon feed stream. Asused herein the Bromine Index of the hydrocarbon streams or mixtures isdetermined using method UOP304. In another embodiment, the inventionremoves at least about 30 wt % of the diolefin compounds from thehydrocarbon feed stream; and the invention may remove at least about 50wt % or at least about 80 wt % of the diolefin compounds from thehydrocarbon feed stream. Herein, the diolefin content of the hydrocarbonstreams or mixtures is determined by method UOP980. Unless otherwisenoted, the analytical methods used herein such as UOP304 and UOP980 areavailable from ASTM International, 100 Barr Harbor Drive, WestConshohocken, Pa., USA.

In another embodiment, the invention further comprises passing at leasta portion of the treated hydrocarbon stream to a nitrogen removal zone,the nitrogen removal zone producing an alkylation substrate streamhaving a lower concentration of the nitrogen compound relative to thetreated hydrocarbon stream. As discussed above, various methods are wellknown in the art to remove nitrogen compounds from aromatic hydrocarbonstreams. See, for example, U.S. Pat. No. 7,205,448; U.S. Pat. No.7,744,828; U.S. Pat. No. 6,297,417; each of which is herein incorporatedby reference in its entirety. In brief, the treated hydrocarbon streamis introduced to the nitrogen removal zone which includes at least oneadsorbent effective to remove nitrogen. Suitable adsorbents includeclays, resins, and zeolites. Typically, the clay and zeolite adsorbentsare acidic. The nitrogen removal zone may comprise two adsorbents suchas a clay or resin adsorbent being located upstream of a zeoliteadsorbent so the treated hydrocarbon stream contacts the clay or resinadsorbent first to produce an intermediate stream which then contactsthe zeolite adsorbent. Different operating conditions includingtemperatures and the amount of water present have been disclosed fordifferent adsorbents and the use of multiple adsorbents in the nitrogenremoval zone.

In an embodiment, the treated hydrocarbon stream is contacted with anadsorbent comprising an acidic molecular sieve at nitrogen removalconditions to produce the alkylation substrate stream having a reducednitrogen content. In an embodiment the molecular sieve is a zeolite.Well known zeolites that may be used include chabazite, also referred toas Zeolite D, clinoptilolite, erionite, faujasite, Zeolite Beta (BEA),Zeolite Omega, Zeolite X, Zeolite Y, MFI zeolite, Zeolite MCM-22 (MWW),ferrierite, mordenite, Zeolite A, Zeolite P, and UZM-8 type zeolitesreferenced below. In an embodiment, the nitrogen removal conditionscomprise a temperature ranging from at least about 120° C. to about 300°C., and the presence of water in an amount ranging from about 20 ppm toabout 500 ppm relative to the treated hydrocarbon stream on a weightbasis.

In another embodiment, the invention further comprises passing at leasta portion of the alkylation substrate stream from the nitrogen removalzone to an alkylation zone wherein the portion of the alkylationsubstrate stream and an alkylating agent are contacted with analkylation catalyst to produce an alkylated benzene product.

In the selective alkylation of aromatics alkylation substrate by anolefinic alkylating agent as catalyzed by an acidic catalyst, theolefins may contain from 2 up to at least 20 carbon atoms, and may bebranched or linear olefins, either terminal or internal olefins. Thus,the specific nature of the olefin is not particularly important. Whatthe alkylation reactions share in common is that the reactions areconducted under at least partially liquid phase conditions, a criterionreadily achieved for the lower members by adjusting reaction pressures.Among the lower olefins, ethylene and propylene are the most importantrepresentatives. An olefinic feed stream comprising an alkylating agentmay include ethylene and/or propylene. Typically, an olefinic feedstream comprising propylene will be at least 65 wt % pure and anolefinic feed stream comprising ethylene will be over 80 wt % pure.Among the remaining olefins, the class of detergent range olefinsconsisting of linear olefins containing from 6 up through about 20carbon atoms which have either internal or terminal unsaturation is ofparticular interest. Linear olefins containing from 8 to 16 carbon atomsand especially those containing from 10 up to about 14 carbon atoms areparticularly useful as detergent range olefins. Alkylation agents mayalso be provided by alkyl constituents of a polyalkylbenzene in atransalkylation reaction zone. Diethylbenzene, triethylbenzene anddiisopropylbenzene are prominent examples of polyalkylbenzenes that canprovide such alkylation agents.

A wide variety of catalysts can be used in the alkylation reaction zone.Suitable catalysts for use in the alkylation zone include catalysts thatdo not suffer deleterious effects from the presence of water.Preferably, a substantial quantity of water may be tolerated or desiredin the presence of the alkylation catalyst. A substantial quantity ofwater preferably means a water concentration in the reactants enteringthe alkylation zone of at least 50 wppm. The alkylation reaction zonemay have a water content of as little as 20 wppm, to over 200 wppm andup to 1000 wppm or more. The preferred catalyst for use in thisinvention is a zeolitic catalyst. The catalyst of this invention willusually be used in combination with a refractory inorganic oxide binder.Preferred binders are alumina or silica. Suitable zeolites includezeolite beta described in U.S. Pat. No. 5,723,710, ZSM-5, PSH-3, MCM-22,MCM-36, MCM-49, MCM-56, type Y zeolite, and UZM-8, which includes thealuminosilicate and substituted aluminosilicate zeolites described inU.S. Pat. No. 6,756,030 and the modified UZM-8 zeolites, such as,UZM-8HS which are described in U.S. Pat. No. 7,091,390. Each of U.S.Pat. No. 6,756,030 and U.S. Pat. No. 7,091,390 is herein incorporated byreference in its entirety.

The basic configuration of a catalytic aromatic alkylation zone is knownin the art. The feed aromatic alkylation substrate and the feed olefinalkylating agent are preheated and charged to generally from one to fourreactors in series. Suitable cooling means may be provided betweenreactors to compensate for the net exothermic heat of reaction in eachof the reactors. Suitable means may be provided upstream of or with eachreactor to charge additional feed aromatic, feed olefin, or otherstreams (e.g., effluent of a reactor, or a stream containing one or morepolyalkylbenzenes) to any reactor in the alkylation zone. Eachalkylation reactor may contain one or more alkylation catalyst beds. Theinvention encompasses dual zone aromatic alkylation processes such asthose as described in U.S. Pat. No. 7,420,098 which is hereinincorporated by reference in its entirety.

The particular conditions under which the alkylation reaction isconducted depends upon the aromatic compound and the olefin used. Onenecessary condition is that the reaction be conducted under at leastpartial liquid phase conditions. Therefore, the reaction pressure isadjusted to maintain the olefin at least partially dissolved in theliquid phase. For higher olefins the reaction may be conducted atautogenous pressure. The alkylation conditions usually include apressure in the range between about 1379 kPa(g) and 6985 kPa(g). In anembodiment, the pressure ranges between about 2069 kPa(g) and 4137kPa(g). The alkylation of the aromatic compounds with the olefins in theC2 to C20 range can be carried out at a temperature of about 60° C. toabout 400° C., and preferably from about 90° C. to about 250° C., for atime sufficient to form the desired product. In a continuous processthis time can vary considerably, but is usually from about 0.1 to about8 hr⁻¹ weight hourly space velocity (WHSV) with respect to the olefin.As used herein, weight hourly space velocity of a component means theweight flow rate of the component per hour divided by the catalystweight in the same units of measure. In particular, the alkylation ofbenzene with ethylene can be carried out at temperatures of about 150°C. to about 250° C. and the alkylation of benzene with propylene at atemperature of about 90° C. to about 200° C. The ratio of alkylatablearomatic compound to olefin used in the instant process will depend uponthe degree of monoalkylation desired as well as the relative costs ofthe aromatic and olefinic components of the reaction mixture. Foralkylation of benzene by propylene, the benzene-to-olefin molar ratiomay be as low as about 0.1 and as high as about 10, with a ratio ofabout 0.5 to about 3 being preferred. Where benzene is alkylated withethylene a benzene-to-olefin ratio may be between about 0.1 and 10, witha ratio of about 0.5 to about 4 being preferred. For detergent rangeolefins of C6 to C20, a benzene-to-olefin ratio of between about 5 andabout 30 is generally sufficient to obtain the desired monoalkylationyield, with a range between about 8 and about 20 even more preferred.

The alkylation reaction zone will often provide a wide variety ofsecondary by-products. For example, in the alkylation of benzene withethylene to produce ethylbenzene, the reaction zone can also produce di-and triethylbenzene in addition to other ethylene condensation products.Similarly, in the alkylation of benzene with propylene to producecumene, the reaction zone can produce di- and triisopropylbenzene inaddition to still more condensation products. As is well known in theart, these polyalkylated aromatics may contact additional aromaticsubstrate in a transalkylation zone to produce additional monoalkylatedproduct. See e.g. U.S. Pat. No. 7,622,622 and U.S. Pat. No. 7,268,267.Further, since transalkylation reactions occur in an alkylation reactionzone and alkylation reactions occur in a transalkylation reaction zone,both zones may be referred to as alkylation zones. Thus, as used herein,the term “alkylation zone” encompasses a transalkylation zone. In anembodiment, the alkylated benzene product comprises at least one ofethylbenzene and cumene.

In a further embodiment, the invention is a method for producing analkylated benzene compound. The method comprises contacting ahydrocarbon feed stream comprising benzene, an organic nitrogencompound, and a diolefin compound with activated carbon. Optionally, thediolefin compound has from four to six carbon atoms per molecule.Contacting conditions comprise a temperature of at least about 50° C.and the presence of water in an amount of at least about 50 ppm relativeto the hydrocarbon feed stream on a weight basis. The contacting stepremoves the diolefin compound and produces a treated hydrocarbon streamhaving a lower concentration of the diolefin compound than thehydrocarbon feed stream. At least a portion of the treated hydrocarbonstream is passed to a nitrogen removal zone, which removes the organicnitrogen compound and produces an alkylation substrate stream having alower concentration of the organic nitrogen compound relative to thetreated hydrocarbon stream. At least a portion of the alkylationsubstrate stream is passed to an alkylation zone wherein the portion ofthe alkylation substrate stream and an alkylating agent are contactedwith an alkylation catalyst to produce an alkylated benzene compound. Inan embodiment, the alkylated benzene compound is a monoalkylated benzenecompound, which may comprise at least one of ethylbenzene and cumene. Inan embodiment, the contacting temperature ranges from about 100° C. toabout 300° C.

Example 1

As a comparative example, a commercially available acid treated clayadsorbent was obtained from Sud-Chemie under the product name TONSIL CO630 G.

Example 2

In accord with the invention, a commercially available activated carbonwas obtained from Calgon under the product name.

Example 3

As a comparative example, a sample of a steam modified ammonium ionexchanged Y zeolite was slurried in a 15 wt % NH₄NO₃ aqueous solutionand the solution temperature was brought up to 75° C. (167° F.). Thesteam modified ammonium ion exchanged Y zeolite is a stabilized sodium Yzeolite with a bulk Si/Al₂ ratio of approximately 5.2, a unit cell sizeof approximately 24.53, and a sodium content of approximately 2.7 wt %calculated as Na₂O on a dry basis. The steam modified ammonium ionexchanged Y zeolite is prepared from a sodium Y zeolite with a bulkSi/Al₂ ratio of approximately 4.9, a unit cell size of approximately24.67, and a sodium content of approximately 9.4 wt % calculated as Na₂Oon a dry basis that is ammonium exchanged to remove approximately 75% ofthe Na and then steam de-aluminated at approximately 600° C. (1112° F.)by generally following steps (1) and (2) of the procedure described incol. 4, line 47 to col. 5, line 2 of U.S. Pat. No. 5,324,877. After 1hour of contact at 75° C. (167° F.), the slurry was filtered and thefilter cake was washed with an excessive amount of warm de-ionizedwater. These NH₄ ⁺ ion exchange, filtering, and water wash steps wererepeated two more times, and the resulting filter cake had a bulk Si/Al₂ratio of 5.2, a sodium content of 0.13 wt % calculated as Na₂O on a drybasis, a unit cell size of the 24.572 {acute over (Å)} and an absoluteintensity of 96 as determined X-ray diffraction. The resulting filtercake was dried to an appropriate moisture level, mixed withHNO₃-peptized Pural SB alumina to give a mixture of 80 parts by weightof zeolite and 20 parts by weight Al₂O₃ binder on a dry basis, and thenextruded into 1.6 mm diameter cylindrical extrudate. The extrudate wasdried and calcined at approximately 600° C. for one hour in flowing airto obtain a comparative zeolite adsorbent having a unit cell size of24.494 {acute over (Å)}, an XRD absolute intensity of 61.1, and 57.2%framework aluminum as a percentage of the aluminum in the modified Yzeolite.

Example 4

A sample of a commercial benzene recycle stream (>99 wt % benzene)containing olefin, diolefin and nitrogen compounds was used as iswithout drying or other treatments as the hydrocarbon feed to evaluatethe effectiveness of the adsorbents of Examples 1-3 to remove theunsaturated aliphatic compounds. The analysis of the feed is reported inTable 1 with the analysis of the effluent or product from each test. Theunsaturated aliphatic content was determined by Bromine Index methodUOP304. The diolefin content was determined by UOP980 as modified toimprove the sensitivity of the method to detect lower levels ofdiolefins. UOP980 was followed except that sample size was altered andstandard solutions of lower concentrations were used during calibrationof the instrument as known by those skilled in the art to improvedetection of lower concentrations of the diolefins in the samples. Themodification of UOP980 does not alter the relative measurements betweendifferent samples, but improves and/or enables quantification ofconcentrations of less than 500 ppm-wt and especially less than 100ppm-wt of diolefins. The commercial benzene recycle stream also includedwater at about the saturation level so the contacting conditionsincluded an amount of water ranging from about 600 ppm to about 800 ppmrelative to the hydrocarbon feed stream on a weight basis.

Prior to each test, the adsorbent was pre-dried at 250° C. for 4 hoursin flowing nitrogen. The adsorption experiment was done in an autoclave,which was first purged with nitrogen followed by charging 0.6 g ofadsorbent and 30 g of the hydrocarbon feed. The autoclave was thenpressurized to about 400 psig and ramped to the temperature listed inTable 1 for each test. The autoclave includes a mixer which was set at100 rpm. When the specified temperature was reached, the autoclave washeld at temperature for one hour with mixing. Thereafter, the heat wascut to allow the autoclave to cool to room temperature and mixingstopped. The spent adsorbent was separated from the liquid product oreffluent, which was sampled and analyzed.

TABLE 1 Feed Example 1 Example 2 Example 3 Temperature, 100 125 150 100125 150 25 75 125 ° C. Bromine 292 138 91 47 189 138 NA 114 91 23 Index,mg Br per 100 g Diolefins, 825 25 3 1 550 340 92 NA 247 5 ppm-wtUnsaturated 53 69 84 35 53 NA 61 69 92 aliphatics removed, % based onBromine Index Diolefins 97 99.6 99.9 33 59 89 NA 70 99.4 removed, wt %

The data demonstrate, each material of Examples 1-3 is effective forremoving unsaturated aliphatic hydrocarbons, as determined by BromineIndex, and for removing diolefins. The activated carbon of Example 2according to the invention, exhibited similar selectivity for removingunsaturated aliphatic hydrocarbons as for removing diolefins withgreater amounts being removed at higher contacting temperatures.

The invention claimed is:
 1. A method for treating a hydrocarbon feedstream comprising an aromatic compound, a nitrogen compound, and anunsaturated aliphatic compound, the method comprising: contacting thehydrocarbon feed stream with an absorbent comprising activated carbon atcontacting conditions including a temperature of at least about 50° C.and the presence of water in an amount of at least about 50 ppm relativeto the hydrocarbon feed stream on a weight basis to remove theunsaturated aliphatic compound and produce a treated hydrocarbon stream;passing at least a portion of the treated hydrocarbon stream to anitrogen removal zone including a nitrogen removal adsorbent to producean alkylation substrate stream having a lower concentration of thenitrogen compound relative to the treated hydrocarbon stream; andpassing at least a portion of the alkylation substrate stream to analkylation zone wherein the portion of the alkylation substrate streamand an alkylating agent are contacted with an alkylation catalyst toproduce an alkylated aromatic compound.
 2. The method of claim 1 whereinwater is present in an amount equal to or exceeding the saturation pointof the hydrocarbon feed stream at the contacting conditions.
 3. Themethod of claim 1 wherein water is present in an amount ranging fromabout 300 ppm to about 800 ppm relative to the hydrocarbon feed streamon a weight basis.
 4. The method of claim 1 wherein the temperature isat least about 100° C.
 5. The method of claim 1 wherein the temperatureranges from about 100° C. to about 300° C.
 6. The method of claim 1wherein the temperature ranges from about 125° C. to about 300° C. 7.The method of claim 1 wherein the contacting conditions further includea pressure ranging from about 34.5 kPa(g) to about 4136.9 kPa(g).
 8. Themethod of claim 1 wherein the hydrocarbon feed stream has a nitrogencontent ranging from about 1 ppm-wt to about 10 ppm-wt.
 9. The method ofclaim 1 wherein the aromatic compound is benzene and is present in anamount ranging from about 5 wt % to about 99.9 wt % of the hydrocarbonfeed stream.
 10. The method of claim 1 wherein the nitrogen compound isan organic nitrogen compound selected from the group consisting of basicorganic nitrogen compounds, nitriles, and mixtures thereof.
 11. Themethod of claim 10 wherein the organic nitrogen compound is present inan amount ranging from about 30 ppb-wt to about 1 mole % of thehydrocarbon feed stream.
 12. The method of claim 1 wherein theunsaturated aliphatic compound is a diolefin compound.
 13. The method ofclaim 12 wherein the diolefin compound is selected from the groupconsisting of butadienes, pentadienes, methylbutadienes, hexadienes,methylpentadienes, dimethylbutadienes, acetylenes, and mixtures thereof.14. The method of claim 12 wherein the diolefin compound is selectedfrom the group of diolefins consisting of C4 diolefins, C5 diolefins, C6diolefins and mixtures thereof.
 15. The method of claim 14 wherein thediolefin compound is present in an amount ranging from about 30 ppb-wtto about 3000 ppm-wt of the hydrocarbon feed stream.
 16. The method ofclaim 14 wherein at least about 30 wt % of the diolefin compound isremoved from the hydrocarbon feed stream on a weight basis.
 17. Themethod of claim 1 wherein the treated hydrocarbon stream has a BromineIndex of at most about 50% of the Bromine Index of the hydrocarbon feedstream.
 18. The method of claim 1 wherein the alkylated benzene productaromatic compound comprises at least one of ethylbenzene and cumene. 19.A method for producing an alkylated benzene compound comprising: (a)contacting a hydrocarbon feed stream comprising benzene, an organicnitrogen compound, and a diolefin compound with an absorbent comprisingactivated carbon at contacting conditions including a temperature of atleast about 50° C. and the presence of water in an amount of at leastabout 50 ppm relative to the hydrocarbon feed stream on a weight basisto remove the diolefin compound and produce a treated hydrocarbonstream; (b) passing at least a portion of the treated hydrocarbon streamto a nitrogen removal zone including a nitrogen removal adsorbent toproduce an alkylation substrate stream having a lower concentration ofthe organic nitrogen compound relative to the treated hydrocarbonstream; and (c) passing at least a portion of the alkylation substratestream to an alkylation zone wherein the portion of the alkylationsubstrate stream and an alkylating agent are contacted with analkylation catalyst to produce the alkylated benzene compound.
 20. Themethod of claim 19 wherein the contacting temperature is at least about100° C.